40 years ago, before gene sequencing was really practical and efficient, biology was in a similar state to:- Astronomy, before Kepler's Laws- Chemistry, before development of the periodic table- ie lacking a coherent basis for understanding what is going on

Now that gene sequencing is much more affordable, we can see the places where genes reside (and some non-coding regions), but we don't know what most of them do. This is like filling in the holes when:- Astronomy: You have some planets you know about, but there are hints that there may be more out there...- Chemistry: You have a periodic table, but it has gaps you are trying to fill

But, like other sciences, biology plays out at many levels - you can have a qualitative understanding of one level, which becomes a deeper understanding when you understand the adjacent levels:- Biology: You can see and understand the behavior of whole organisms, but it becomes more complete when you understand cells - and even better when you can read the DNA- Astronomy: You can see the stars, but you understand them better when you understand how nuclear fusion works- Chemistry: You can understand mixing chemicals in the lab, but you understand it better when you know about atoms, and even better when you understand the quantum behavior of electrons and nuclei.

However, we are still making slow progress on the most complicated level of biology - whole ecosystems. We can see the individual organisms, but how they will interact in the future is beyond us...

If you require a field of science to have terminology that is completely unambiguous and universally accepted by everyone, I don't think you'll find a single field that fits the bill. Chemistry has oligomers and polymers, which do not have any hard line separating the two. Astronomy has planets, which are still not unambiguously defined despite the definition that was finally derived for them not all that long ago (just how cleared does the orbit have to be? Just how close to hydrostatic equilibrium is necessary?). The classification of rocks in geology has blurry boundaries.

I think a distinction needs to be made between "well-defined" and "sufficiently well-defined". If an evolutionary biologist is experimenting to see how long it takes for two separate populations of fruit flies to become reproductively isolated from each other, they can define "species" to suit that particular experiment and it will be good enough to get useful results out of it.

Of course, we could accept that, since little or nothing is ever precisely defined, nothing is science.At that point we need to coin a new word for "All the stuff that we used to call science, but it upset sim".